Drooped cellular covering for architectural openings

ABSTRACT

A covering for an architectural opening includes a panel of material consisting of a first flexible sheet of material on which a second flexible sheet of material is secured along vertically spaced horizontal lines of attachment so that the second sheet of material billows or flexes away from the first sheet of material to define a plurality of vertically superimposed cells. The creases placed in the cells are designed so that as the panel of material is wrapped around a roller, the creases are reinforced to extend the life of the creases and thus the desired billowing effect of the cellular panel of material. Various systems are disclosed for extending and retracting a panel of material as well as for anchoring the top and bottom edges of the panel to a roller in a manner so that they can be easily attached/detached without disassembling the hardware for the covering.

CROSS REFERENCE TO RELATED APPLICATION

This application is a non-provisional application claiming priority to U.S. provisional application Ser. No. 60/640,015, filed Dec. 30, 2004, the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to cellular coverings for architectural openings and particularly those utilizing a panel of material formed from two sheets of fabric that are interconnected along horizontal lines of attachment with one sheet defining expanded but drooped cells off a confronting face of the other sheet. The cells are uniquely creased and interconnected to encourage the cells to retain an expanded form. A system for rolling the shade on a roller is also disclosed which encourages a retention of the expanded cellular form, once the panel is unrolled. A system is further disclosed for attaching the top edge and the bottom edge of a panel of material to rollers so the panel can be easily inverted if desired.

2. Description of the Relevant Art

Retractable coverings for architectural openings are in common use and include by way of example venetian blinds, vertical blinds, roll-up shades, cellular shades, and the like. Some cellular shades are transversely collapsible and are raised and lowered similarly to a venetian blind while other collapsible shades are retractable about rollers. An example of the later type disclosed in U.S. Pat. No. 5,603,368 which is of common ownership with the present application.

Improvements in roll-up cellular shades are continually being made and it is to provide an alternative to conventional roll-up cellular shades that the present invention has been developed.

SUMMARY OF THE INVENTION

The cellular panel of the present invention includes a back-up or support structure such as a sheet of flexible material to which a second sheet is attached along vertically spaced horizontal lines of attachment to define a plurality of vertically spaced horizontally extending expanded cells. The second sheet is creased at two locations to form each cell into a generally D-shaped cross-sectional configuration having a rounded soft-hanging curvature. The creases in the cells encourage the cells to be expanded when the panel of material is extended across all or a portion of an architectural opening. The panel can be retracted by rolling it around a roller at the top or bottom of the architectural opening and the creases in the second sheet of fabric are formed so as to be reinforced by being repeatedly folded consistent with the direction of the creases each time the panel is wrapped around a roller.

A method of creasing the second sheet of material during the formation of the panel of material is disclosed with the creased sheet of material being formed in a shoe that is divided between heating and cooling components. In the heating component, the fabric is drawn into the desired folded configuration and compressed between the heated confronting shoe component and a cylindrical mandrel to form the creases and then the material is cooled as it is drawn between the mandrel and the cooling component to set the creases.

Several embodiments for retracting the panel of material about rollers are disclosed with each system folding the panel on a roller in a manner to reinforce the creases formed in the second sheet of material so as to encourage the cellular panel to remain expanded each time the covering is extended.

A unique system for quickly inverting the panel of material by flip flopping the top and bottom edges of the panel is also shown which could be used with most roll-up coverings.

Other aspects, features and details of the present invention can be more completely understood by reference to the following detailed description of a preferred embodiment, taken in conjunction with the drawings and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary vertical section taken through a panel of material used in a covering in accordance with the present invention with the panel of material shown in an extended position.

FIG. 1A is an isometric of a covering in accordance with the present invention utilizing the panel of material shown in FIG. 1.

FIG. 2 is a vertical diagrammatic section taken through a shoe in which the panel of material shown in FIG. 1 can be formed.

FIG. 3 is an enlarged fragmentary vertical section taken through a lower portion of the covering of FIG. 1A.

FIG. 4 is an isometric similar to FIG. 1A showing a second embodiment of the covering of the present invention.

FIG. 5 is an isometric looking at the rear of the covering of FIG. 4.

FIG. 5A is an enlarged section taken along line 5A-5A of FIG. 5.

FIG. 5B is an enlarged section taken along line 5B-5B of FIG. 5.

FIG. 6 is a fragmentary elevation of a roller in which the top or bottom edge of a panel of flexible material is secured with a semi-rigid strip of material illustrating a method of attachment/detachment.

FIG. 7 is a section taken along line 7-7 of FIG. 6.

FIG. 8 is a bottom plan view illustrating the roller of FIG. 6.

FIG. 9 is a fragmentary vertical diagrammatic section through an alternative system for extending and retracting a flexible panel of material in a top down/bottom up environment with the covering partially extended.

FIG. 10 is a fragmentary section similar to FIG. 9 with the covering fully retracted.

FIG. 11 is a fragmentary section similar to FIG. 9 with the covering fully extended.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 1A, a covering 12 incorporating a panel 14 of cellular material in accordance with the present invention is shown to include a head rail 16, the panel 14 of cellular material with cells 15 anchored at its top edge to the head rail and at its bottom edge to a bottom roller 20, a pair of looped lift cords 22, and an endless drive or control cord 24.

As is probably best seen in FIG. 1, the panel 14 of cellular material is comprised of a support structure which could be a first sheet 26 of backing or support material and a second sheet 28 of looped and creased material that is secured to the first sheet along vertically spaced horizontal lines of attachment 30 in any suitable manner such as with adhesive, ultrasonic bonding or the like. The sheets of material 26 and 28 can be the same or different and can, by way of example, be a sheer fabric, a translucent material, or even an opaque material. Both sheets of material are flexible with at least the second sheet of material being semi-rigid and creasable. The second sheet has enough rigidity to retain the full expanded shape shown in FIG. 1. A suitable fibrous material made with a thermo-forming resin is well suited for at least the second sheet of material with thermoset or thermoplastic resins being acceptable binders for the fibers. The support structure would not necessarily have to be a sheet of material 26 but could be for example, a plurality of vertical cords or micro fibers (not shown) to which the second sheet is attached.

Each cell 15 constitutes an elongated tube of generally D shaped cross section and with each elongated cell overlying a next adjacent lower cell and being identical therewith. Each cell includes a first inwardly directed or pointed crease 32 along the lower edge of its upper line of attachment 30 and a relatively straight upper segment 34 extending from the first crease to a second outwardly directed or pointed crease 36. The first segment 34 of the cell which might be referred to as a top wall, slopes downwardly at a small acute angle (e.g. between 5° and 45°) to the second crease. A second segment 38 of the cell which might be referred to as a front wall hangs downwardly in a soft drooping or looped fashion from the second crease in a soft hanging curve and is substantially vertically directed. A third segment 40 or bottom wall of the cell extends from a curved and drooped lower edge 42 of the front wall substantially horizontally and rearwardly to the next lower line of attachment 30. The bottom wall is of generally S shaped configuration. The outwardly pointed or directed second crease 36 as well as the first crease 32 serve to assist in supporting the cell in the fully expanded configuration illustrated in FIG. 1, which of course is facilitated further by the semi-rigid character of the material from which the second sheet 28 is made. By making the second sheet from a thermo-forming resin material in which fibers are imbedded, the sheet is resilient in that even after having been deformed as when the material is wrapped around a roller, it will return dependably to the form or configuration shown in FIG. 1. This is particularly true, due to the nature in which the material is wrapped around the bottom roller 20, as will be described in more detail hereafter.

The panel 14 can be formed in numerous ways, but it has been found desirable to make the panel by first securing the second sheet of material 28 to the first sheet of material 26 along the lines of attachment 30 so the second sheet of material is looped off a front face of the first sheet of material i.e., there is more of the second sheet of material between lines of attachment than of the first sheet of material. The double-layered panel can then be pulled around a mandrel 44 (FIG. 2) beneath a pair of generally semi-cylindrical compressive shoes 46 and 48 which are yieldingly forced against the opposed faces of the mandrel with coil springs 50. One shoe 46 is heated in a conventional manner such as with a hot fluid passed through internal passages 52 in the shoe while the other shoe 48 is cooled as with a cooling fluid passed through passages 52 in the shoe.

When the panel of material 14 is pulled into the space between the mandrel 44 and the compressive shoes 46 and 48 as shown in FIG. 2, the first sheet of material 26 passes smoothly around the mandrel in a counterclockwise direction while the second sheet of material 28 is laid smoothly against the first sheet of material from a first line of attachment 30 downwardly but as the panel is advanced around the mandrel, the second sheet of material is continuously forced into a smaller and smaller loop until it defines the two creases 32 and 36 and an overlapped fold 54 of generally S-shaped configuration. The overlapped fold is confined between the mandrel and the compressive shoes with the heated shoe forming the creases in the material along the overlapped fold and the cooling shoe setting the creases before the panel of material exits the mandrel. The fold 54 defines overlapping layers of the second sheet of material which includes a line of attachment 30 in the top wall 34 and a top portion of the front wall 38 of a cell 15. The creases surge the second sheet of material to expand or billow away from the first sheet of material to establish the desired D-shape of the cell as shown in FIG. 1. The first crease 32 is secured to the first sheet of material 26 while the second crease 36 is allowed to billow or flex away from the first crease along the first segment or top wall 34 of the cell again as fully appreciated by reference to FIG. 1.

Referring to FIGS. 1A and 3, it will be appreciated the panel of material 14 is secured along an upper edge 56 in a fixed relationship and in any suitable manner to the head rail 16. Preferably the upper edge is concealed within the head rail for aesthetic purposes. The bottom edge 58 of the panel 14 is anchored to the bottom roller 20 of the covering, which is generally cylindrical in configuration, having a longitudinal channel 60 formed in an outer surface thereof defining a relatively small slot 62 in the outer surface between a pair of opposed lips 64. The lower edge of the panel is hemmed and a rigid or semi-rigid anchor strip 66 is positioned within the hem. The anchor strip with the hem may be slid axially along the length of the roller 20 from one end to the other to secure the lower hemmed edge of the panel to the bottom roller in a conventional manner. The bottom edge could also be secured to the roller in an alternative manner as will be described hereafter.

The bottom roller 20 is rolled in a counterclockwise direction as viewed in FIG. 3 when retracting the covering from the extended position of FIG. 1A to a fully retracted position wherein the bottom roller is disposed adjacent to the head rail 16. The bottom roller is rolled with the looped lift cords 22 which are anchored at a front end 68 (FIG. 1A) to a concealed location at the front of the head rail and at a back end 70 to a take-up roller 72 in the head rail. The take-up roller is rotated with the endless control cord 24 by moving the control cord in a rotating direction to thereby correspondingly rotate the take-up roller allowing the lift cords 22 to be wrapped therearound. In this manner, the size of the loop of the lift cords is adjustable from a maximum size when the shade is fully extended as shown in FIG. 1A, to a minimum size when the covering is fully retracted. The rotation of the bottom roller occurs through friction between the lift cords and the panel of material 14 with the lift cords engaging the panel of material around the underside of the bottom roller 20. As the lift cords are raised along the back of the panel, the shortening of the loop of lift cords causes the bottom roller to be raised while it is being rotated in a counterclockwise direction thereby wrapping the panel of material thereabout. This type of lift system is common in bamboo shades wherein horizontal slats of bamboo are interconnected with elongated vertical cords and the bottom rail is raised with endless lift cords as described above.

As is best illustrated in FIG. 3, as the bottom roller 20 is rotated in a counterclockwise direction, the panel of material 14 is wrapped therearound with the second crease 36 in the panel being encouraged from the configuration of the panel to overlap and form a fold 74 configured identically to the fold 54 in the material as it exits the compressive shoes 46 and 48 as shown in FIG. 2. The second sheet of material 28 in the panel is compressed by the lift cords 22 as the panel is initially wrapped onto the bottom roller. The free-hanging soft loop in the front wall 38 of each cell 15 in the second sheet of material adjacent to the bottom of each cell is also forced to fold at 76 in an opposite direction to the second crease 36 and toward an overlying relationship with the preceding or underlying line of attachment 30. Accordingly, as seen in FIG. 3, there are two folds 74 and 76 established as the panel of material wraps around the bottom roller with the folds being directed toward each other and in overlying relationship with a line of attachment 30.

As will be appreciated, inasmuch as the first and second creases 32 and 36 are compressed into their original configuration shown in FIG. 2 as they are wrapped around the bottom roller in the fold 74, the creases are reinforced each time the panel of material is wrapped around the roller. In this manner, the creases in the second sheet of material are reinforced continually upon operation of the covering encouraging the second sheet to fully deploy to the expanded position shown in FIG. 1 with repeated use and over long periods of time.

As will be appreciated, the upper edge 56 of the panel of material 14, which is secured to the head rail 16, could be secured to an upper roller (not shown) which is not rotatable but rather statically positioned within the head rail but wherein the upper edge is secured to that roller identically to the manner in which it is secured to the bottom roller 20, i.e. with a hem and a rigid or semi-rigid anchor strip inserted within the outwardly opening channel 60 of the roller. This system for anchoring the upper edge of the fabric is useful in accordance with features of the present invention which will be described in more detail hereafter.

FIGS. 4-5B show an alternative embodiment of the present invention wherein the panel of material 14 is identical to that previously described and wherein the upper edge 56 of the panel of material is secured as with adhesive or the like to the head rail 16 and the bottom edge 58 is secured to the bottom roller 20 in a manner identically to that previously described. In this embodiment of the invention, however, the lift cords have been replaced with lift straps 78 at opposite ends of the panel 14 with the front end 80 of each lift strap being secured preferably in a confined location to the head rail and a rear end 82 of the lift strap being anchored to a spool 84 fixed for unitary rotation with a take-up rod 86. The take-up rod is supported by a pair of brackets 88 fixed to the head rail and is rotated with an endless control cord 24 with the upper end of the endless control cord 24 being confined within a housing 90 and frictionally engaged with the take-up rod for unitary rotation therewith. In other words, as the control cord is rotated, the take-up rod is simultaneously rotated along with the spools anchoring the rear ends of the lift straps 78.

A pair of guide straps 92 have their upper ends 94 secured to the take-up rod 86 and their lower ends 96 secured to a guide rod 98. The guide rod as shown in FIG. 5A has a slot 100 at each end thereof which slidably receives an associated lift strap 78 and a second slot 102 spaced inwardly thereof for anchoring the lower end of an associated guide strap 92. As seen in FIG. 5B, the lower ends 104 of the guide straps are hemmed and a rigid rod 106 is inserted therethrough and seated in a recess 108 communicating with the associated slot 102.

As the take-up rod is rotated with the control cord 24, the guide straps 92 are wrapped around the take-up rod 86 on a smaller diameter than the lift straps 78 so that the guide straps will lift the guide rod 98 at about the same speed as the bottom roller 20 is being raised by the lift straps inasmuch as the lift straps pass around a greater and increasing diameter of the bottom roller as the panel of material accumulates thereon. The guide rod therefore retains the position of the lift straps as the covering is moved between retracted and extended positions.

With reference to FIGS. 6-8, a system is shown for easily connecting and/or disconnecting a hemmed edge 110 of a panel of material 112 to/or from an elongated element such as a roller 114 of the type described previously. The panel could be any flexible panel including a panel 14 of the type previously described herein. The roller as seen in FIG. 7 is of cylindrical configuration having a channel 116 formed therein that opens through a slot 118 in the outer surface of the roller between a pair of confronting lips 120. The confronting lips are uniformly spaced from each other commencing at each end of the cylinder. However, at a centered location along the length of the cylinder, the lips are retracted as shown in FIG. 8 to define a relatively wide gap 122. The wide gap at the longitudinal center of the cylinder or roller 114 is wide enough to allow an anchor strip 124 of semi-rigid material to be removed therefrom while the anchor strip is inserted into the hem 110 along the edge of the panel. When attaching the panel of material 112 to the roller 114, rather than inserting the hem along with the anchor strip into an open end of the channel and sliding the strip along with the hemmed material therealong as is conventional, the ends of the anchor strip 124 with the hem of the panel therearound can be inserted into the gap 122 and forced in opposite directions until the entire anchor strip has been received with the hemmed edge of the material within the channel 116. The hemmed edge of the material can be removed in a reverse manner by grasping the anchor strip with the hemmed material at the location of the wide gap and pulling the semi-rigid strip of anchor material out of the channel as illustrated in FIG. 6.

This system for connecting and disconnecting a panel of material 112 to/or from a roller 114 is useful with any flexible panel of material as the material can be removed from the roller without removing the roller from the hardware of the covering in which it is mounted since the anchor strip does not have to be slid longitudinally out of an open end of the roller but can be removed laterally. This also enables one to easily invert a panel of material should the panel lose its resilience and desired cellular configuration in the case with a cellular panel. The resilience of the panel, of course, permits the cells in the panel to fully expand as desired and as illustrated for example in FIG. 1. In other words, should the material start drooping more than desired, it can be inverted by easily removing the opposite top and bottom edges of the panel from their anchor rollers and after inverting the panel of material reattaching the edges to the opposite anchor rollers as described above without disassembling the hardware for the covering.

As can be appreciated by reference to FIG. 4, the location where the lift straps 78 or in the case of the embodiment of FIG. 1A the lift cords 22, engage the panel of material 14, the panel can become deformed at 126. To avoid such a deformation in the panel, a system of the type shown in FIGS. 9-11 can be utilized. In this embodiment of the invention, the bottom edge 58 of the panel of material is again secured to the bottom roller 20 as described previously so that the panel of material can be wrapped around the bottom roller as the roller is raised and rotated with the lift cords 22 or straps 78. For purposes of the present disclosure, lift cords are utilized but lift straps could be used in lieu of the lift cords. In the embodiment of FIGS. 9-11 and as best appreciated by reference to FIG. 9, there is an upper lift cord 22U and a lower lift cord 22L with the bottom edge 128 of the upper lift cord being secured to the upper edge of an elongated sling or flexible strip of material 130 with a batten 132 that runs along the full length of the strip of material. Similarly, the upper end 134 of the lower lift cord 22L is secured to a batten 136 along the bottom edge of the sling of flexible material 130. The upper lift cord 22U extends around a pulley 138 in the head rail 140 with the lower lift cord 22L extending around a pulley 142 disposed beneath and at a rearwardly displaced position in the head rail relative to the pulley 138. Both the upper and lower lift cords can be manually pulled or released and conventional cleats (not shown) are provided for anchoring the lift cords at any desired location along their length. The panel of covering material 14 has an upper edge 144 adhesively or otherwise secured to the lower cord 22L immediately beneath the batten 136 as seen in FIG. 9 with an anchor bar 146 and the lower or opposite edge of the panel is anchored to the bottom roller 20, for example, in a manner as previously described herein.

When operating the covering so that the panel of material 14 lowers from the head rail 140 as it is being extended across an architectural opening, the upper lift cord 22U is raised to its fullest extent and cleated or anchored in a fixed position as shown in FIG. 1 D and the lower lift cord 22L is allowed to extend so that the panel of material is unrolled from the bottom roller 20 which rotates in a clockwise direction allowing the panel of material to be unwrapped therefrom. Of course, the panel can be fully extended in this manner so as to extend from the lower edge of the sling of flexible material 130 down to its bottom edge which is anchored to the bottom roller. Further, leaving the upper lift cord anchored and shortening the lower lift cord will cause the panel to roll up about the bottom roller to raise the shade to the retracted position of FIG. 1D adjacent to the head rail. As will be appreciated, by raising the panel of material in this manner, the roller will ultimately become horizontally aligned with the sling 130 and as fully appreciated by reference to FIG. 10, the sling will pass beneath the roller and thereby support the roller in the fully retracted position along its full length thereby not deforming the panel 14 as might incur in the embodiments of FIGS. 1A and 4.

The covering of FIG. 9-11 could also be operated by extending both the upper 22U and lower 22L cords with the panel 14 wrapped around the bottom roller 20 and supported by the sling 130 until the bottom roller is positioned adjacent to the lower edge of the architectural opening in which the covering is mounted as shown in FIG. 11. By then lowering the lower cord at a rate simultaneous to that of raising the upper lift cord, the panel will unroll from the bottom roller while the bottom roller remains adjacent to the bottom edge of the architectural opening. Accordingly, the panel of material will extend from the bottom of the opening toward the top of the opening. Of course, the reverse would be applicable to lower the top edge of the panel back to a rolled position about the bottom roller at its lowered location. This would be accomplished by raising the bottom lift cord at the same rate that the upper lift cord is extended.

It will be appreciated that the sling of flexible material 130 can support the bottom roller 20 at any position of the bottom roller by appropriately manipulating the upper 22U and lower 22L lift cords and the sling of material, of course, uniformly supports the roller and panel 14 along its entire length to avoid deformation of the roll of panel material. It should also be appreciated that while the embodiment of the invention shown in FIGS. 9-11 could be used with a panel of material 14 of the type shown in FIGS. 1 and 1A, it can also be used with any flexible panel of material capable of being rolled around a roller.

Although the present invention has been described with a certain degree of particularity, it is understood the disclosure has been made by way of example, and changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims. 

1. A cellular panel for a covering for an architectural opening comprising in combination: a vertically oriented flexible support structure, and a flexible sheet of material secured to said support structure along vertically spaced horizontal lines of connection so as to define a plurality of horizontally disposed elongated cells, said cells including an elongated outwardly directed crease spaced from a line of connection to define a top wall of the cell between the crease and the line of connection and a front wall drooping downwardly from said crease and continuing through a curve to a bottom wall which is connected to said support structure along the next adjacent lower line of connection.
 2. The panel of claim 1 wherein said support structure is a sheet of material.
 3. The panel of claim 1 wherein said cells include a second crease in the opposite direction of said first-mentioned crease.
 4. The panel of claim 3 wherein said second crease is along a line of connection.
 5. The panel of claim 4 wherein said top wall of said cells inclines downwardly away from said support structure at acute angle of less than 45°.
 6. The panel of claim 5 wherein said bottom wall forms substantially a right angle with said support structure.
 7. A covering for an architectural opening comprising in combination: a head rail, at least two flexible looped lift elements having one end secured to said head rail and a second end for manipulation so as to increase or decrease the size of said loop, a bottom roller suspended within said loops of said lift elements, and a cellular panel suspended at an upper end from said head rail and having a lower end secured to said bottom roller, said panel including at least one crease, said bottom roller being rotatable by movement of said lift elements between larger and smaller loops and when said bottom roller is rotated in one direction it causes said panel to be wrapped therearound with said crease being folded on said roller in a reinforcing direction.
 8. The covering of claim 7 wherein said at least one crease is on a second sheet of material in said panel with said second sheet being secured to a first sheet of said panel along parallel spaced lines of attachment to define a plurality of parallel cells between said first and second sheets, a top wall of each of said cells being defined between a line of attachment and said at least one crease, a front wall hanging downwardly from said at least one crease in a drooping curve and a bottom wall between the curved bottom of said front wall and the next lower line of attachment.
 9. The covering of claim 8 wherein said at least one crease is directed outwardly of said cell.
 10. The covering of claim 9 further including a second crease which is inwardly directed along the line of attachment between said top wall and said first sheet.
 11. The covering of claim 9 wherein said second sheet is a resilient material.
 12. The covering of claim 7 wherein said second end of said looped lift elements is secured to a rotatable rod about which said lift elements can be wrapped or unwrapped by rotative movement of said rod, and a control system for reversibly rotating said rod.
 13. The covering of claim 12 wherein said lift elements are cords.
 14. The covering of claim 12 wherein said lift elements are straps.
 15. The covering of claim 12 further including guide straps secured to said rotatable rod for wrapping and unwrapping about said rod with rotation thereof, a guide rod secured to said guide straps for vertical movement in response to wrapping and unwrapping of said guide straps about said rod, said guide rod including slots therethrough for slidable receipt of said flexible elements to guide movement of said flexible elements.
 16. The covering of claim 15 wherein said flexible elements are straps.
 17. A covering for an architectural opening comprising in combination: a head rail, a first flexible lift element operatively associated with said head rail, said first element having a first end and a second end, the second end being manipulatable to raise and lower said first end, a flexible strip of material having a top edge supported by said first end of said first lift element and a bottom edge, a second flexible lift element operatively associated with said head rail, said second element having a first end and a second end, the second end of said second lift element being manipulatable to raise and lower said first end of the second lift element, said first end of said second lift element being connected to said bottom edge of said flexible strip, a rotatable bottom roller suspended by said lift elements and said flexible strip, and a flexible panel secured at a lower edge to said bottom roller and operatively secured at an upper edge to the bottom edge of said flexible strip, whereby upon selected movement of said first and second lift elements, said flexible strip of material can be positioned beneath said bottom roller in supporting relationship therewith.
 18. The covering of claim 17 wherein said bottom roller can be raised and lowered as well as rotated by selective movement of said first and second lift elements.
 19. The covering of claim 18 wherein said flexible strip of material can be positioned beneath said bottom roller in supportive relationship therewith at any raised or lowered position of said bottom roller.
 20. A system for securing an edge of a flexible panel to an elongated element comprising in combination: a flexible panel having a semi-rigid strip of material secured to an edge thereof, and an elongated element having a recessed channel along the length thereof, said channel opening through an elongated slot in said element defined by at least one overhanging lip, said slot having a widened portion at a preselected position along the length of said slot, said widened portion being wide enough for said strip of material to fit through but the remainder of said slot being narrow enough to encapture said strip of material in the channel, whereby said strip of material and secured edge of said panel can be inserted into or removed from said channel through said widened portion.
 21. The system of claim 20 wherein said elongated element is a cylindrical roller and said slot opens through the cylindrical surface thereof.
 22. The system of claim 20 wherein said panel has a hem along said edge thereof and said strip of material is received in said hem.
 23. The system of claim 20 wherein said strip of material has opposite ends and is inserted into said channel by first inserting one or both of said opposite ends through said widened portion and continuing to insert the strip of material until it is fully confined within said channel.
 24. The system of claim 23 wherein said strip of material is removed from said channel by pulling an intermediate portion of said strip of material from said channel and through said widened portion until the entire strip is removed from said channel. 